A method of controlling a foldable pedal device includes an operation of the foldable pedal device, in which both a foldable accelerator pedal and a foldable brake pedal are hidden in an autonomous driving mode, both the foldable accelerator pedal and the foldable brake pedal basically pop up in a manual driving mode, and a one-pedal mode may be implemented such that only one of the foldable accelerator pedal and the foldable brake pedal pops up in the manual driving mode according to a driver's selection.